I wouldn't say that you should be concerned, but I would say that you should be careful. Your goal is to reduce weight. The reduced weight of aluminum comes with the tradeoff of reduced strength compared to steel. However, if you are careful not to over-torque the screws in aluminum threads (so as to strip them) and you respect the fact that aluminum is not as hard as steel, you will probably be alright. I would definitely use a strong threadlock compound on the screws.